Proximity services exist in various forms. In some current prevalent proximity-based services, the devices that broadcast information for a particular service belong to the provider of that service. For instance, a department store that wants to send advertisements about on-sale items must purchase an access point or a subscriber unit capable of sending information assigned to the department store. This means that a business or individual has only coverage within the immediate range of the devices they own and operate.
A most notable proximity service is referred to as geo-fencing, where services can specify a certain geographical area and ask the proximity service provider to notify them when a client enters that specified area. The specified area can be fuzzy (e.g., an area covered by a particular WiFi service set identifier (SSID) or cellular base station) or more explicit by defining explicit geographical boundaries and using a global position system (GPS) or other localization techniques. Another important class of proximity service solutions utilizes relative proximity between pairs of wireless devices, where one, both or none of the devices might be mobile. Implicit in all these services, the discovery is opportunistic, i.e., clients discovering the services should be within the radio range (e.g., <<500 meters) of the service being advertised.
Long Term Evolution (LTE)-Direct, hereinafter referred to as LTE-D, provides a radio modem based service discovery where applications are assigned application specific expressions (e.g., 128 bits) to broadcast their services over dedicated LTE uplink resources allocated by a mobile operator. Once an application publishes one or more expressions, these expressions are pushed down to the LTE-D chip in a wireless user device, or user equipment (UE). When an application subscribes to an expression, it defines which bits of the expression should be used and to what values they need to be equal (i.e., a bit-mask and a match value). The bit-mask and match value are pushed down to the LTE-D chip of a user device. LTE-D chip and LTE radio of the user device periodically wake up, broadcast any published expressions on the user device using some of the LTE uplink resources allocated for service discovery and in the remaining resources for service discovery, they listen to the expressions broadcasted by other devices to identify any matches to the subscribed expressions. When the LTE-D chip in a user device matches any expression, it notifies the application subscribed to that expression on the same device. Upon receiving the notification, the application executes its application logic. Since the operating system and application can be asleep during expression broadcasting and receiving, the system can achieve high energy efficiency.
LTE-D provides a publish-subscribe mechanism through which expressions broadcasted and/or received over a subset of LTE uplink resources for device-to-device (D2D) service discovery. LTE-D also provides mechanisms for receiving static service data from a remote server upon a service is discovered. Qualcomm provides Expression Name Servers (ENS) that handle registration of blocks of expressions by operators and public applications. However, ENS does not explicitly specify how these blocks of expressions are managed and/or handled by specific operators and applications.